Pagine

What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Marantz 1070

The
Marantz Model 1070 stereo console amplifier was designed by American engineers,
but is manufactured under their control in Japan. With a total power output
approaching 100 watts RMS, it is compact in comparison with many competitive
amplifiers, yet has a wide range of facilities.

The
amplifier is fully screened, with a metal housing finished in imitation wood
veneer, and the brushed aluminium front panel is protected by a removable clear
plastic cover. The main controls are mounted on a recessed black anodized panel
with a clear perspex protective cover over the lettering and control
calibrations. This panel is not back illuminated and therefore it is essential
that the panel is placed in a good light. The controls on the front panel are a
large selector knob for phono, tuner, auxiliary, tape 1 and tape 2. Next comes
the tape monitor switch which can select either of two tape machines. In the
centre are three slider-type tone controls for bass, mid-range and treble. To
the right of these controls is the mode selector switch for left, right,
Stereo, stereo reverse, and mono L R, and finally the rotary volume control.
Below the main controls are the following: sockets for stereo microphone and
headphones, push-buttons for low filter, high filter, loudness, main speakers,
remote or ambience speakers, and power on-off. In the centre is the balance
control.

There
are four fuses to protect the amplifier and loudspeakers but to gain access to
these it is neces.snry to remove the outer top cover. The well-designed rigid
chassis carries a heavy Marantz Model 1070 stereo amplifier power transformer,
fully screened. Separate printed circuit boards are used for the stabilized
power supply, the input pre-amplifiers and tone control circuits. The fully
complementary output stages are mounted on heavy heat sinks together with the
penultimate driver stages. Whilst conventional soldering is used on switches,
plugs etc, inter-panel wiring makes use of wrapped joints, a technique claimed
to have a lower contact resistance than soldered joints.

On the
rear panel are eight spring-loaded terminals for the main and remote pairs of
loudspeakers, and below these are a 200W unswitched AC mains flat-contact
American socket and a similar switched 100W one. Normally the pre-amplifier is
directly connected to the power amplifier but, with the gradual use of graphic
equalizers, for example, it is desirable to separate the pre-amplifier from the
power amplifier. In the case of the Marantz 1070 this is achieved by having
left and right 'pre-out' and `main-in' phono sockets on the rear panel. These
automatically bridge together but, when a phono plug is inserted, the internal
connection is interrupted and any external unit can be connected between the
two parts of the amplifier. There are input and output phono sockets for two
separate tape recorders, duplicated with DIN sockets. Finally there are three
pairs of phono sockets for phono, tuner and auxiliary. A 168cm (66-inch)
three-core mains cable is permanently fixed to the amplifier.

Specifications

Gain-Phono (low
level) to pre-amp: 55 dB

Phono to recording
output: 40 dB

High level to
pre-amp output: 15 dB

Input Impedance

Low
level input Phono, Microphone: 47 kΩ

High
level input: >50 kΩ

Input sensitivity

Phono (low): 1,8 mV to equal 1 volt output at pre-amp out

Frequency
Response: 20 - 20,000 Hz; ±1 dB at rated power output

Intermodulation
Distortion: Less than 0,3% at rated
power output (SMPTE)

Damping
Factor (20-20,000 Hz): Greater than 20
into 8Ω load

Total Noise

From
magnetic phono input to power amp output:
Less than 1,5 μV equivalent
input at rated output into 8Ω

Volume
Tracking: Within 3 dB

Rated Power Output
(continuous average per channel, all channels driven)